The unique structural characteristics of composite materials and cost-to-weight ratio make it a valuable commodity across a wide range of industries. Having the most versatile CNC machine may be the best investment.
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A considerable amount of time and investment goes into finding the right CNC solution to efficiently and effectively machine composites. The last thing manufacturers want is to invest in the wrong machine and be paying for that mistake for years to come. With little room for error, it is important to understand how different materials, machinery characteristics, and machinery options affect machining speed, precision, service, and overall production.
High-speed Honeycomb Core Machining. Watch a demo of the C.R. Onsrud E-Series.
Material density plays a key role in determining the best spindle RPM, HP, and torque for an application. To aggressively machine hard materials, such as steel and Inconel® , some traditional machining centers typically are equipped with high torque, low RPM spindles that operate at a maximum of 12,000 RPM. When it comes to composites (such as foam, tooling board, or carbon fiber), a high torque, low RPM spindle is too slow to reach optimal chip load and thus results in inefficient (slower) composite machining. Instead, high RPM (18,000 - 24,000), low torque spindles are more efficient in reducing cycle time, lengthening tool life, and improving overall spindle reliability. For the best of both worlds (composite and nonferrous metal machining), consider a spindle capable of running at 20,000 - 24,000 RPM and higher feed rates for lighter-duty materials but also can operate in the 10,000 - 12,000 range for harder materials that need more torque.
Dust Collection Tray, Optional Vacuum Ports. Remove harmful dust and debris from fully enclosed CNC Machines. Watch the machine walk-thru.
Machining composites often creates a large amount of dust and debris that can cause health problems to workers and damage to the machine. Some composite dusts can lead to lung damage if inhaled and some are electrically conductive, so they can damage machine circuits and cause spindle or machine wear at an increased rate. Thus, choosing a CNC solution with sufficient dust collection and properly sealed and covered components is imperative when working with composites. Some additional considerations for handling abrasive material machining include air knife systems, downdraft tables, and/or full enclosures.
5-Axis Programmable Dust Hood. Watch a demo.
Fully Enclosed CNC Router. Reduce harmful debris and airborne particles. Watch a demo.
Air Knife. Remove Dust & Debris with CNC-Controlled Airblasts. Watch up close.
When machining complex 3D composite components, a 5-axis machine is more efficient than a 3-axis machine and provides a greater return on investment over time. With a 5-axis machine, multiple sides of a part can be machined without having to manually reposition material or swap out tooling for angled heads. A 3-axis machine can perform multi-face machining as well but at a much slower rate as it requires an operator to stop the machine and reposition the part after each operation. To achieve 5-sided milling, drilling, tapping, and/or sawing operations without a 5-axis machine or without having to manipulate parts, consider adding a 4th axis and utilize angled heads, known as aggregates.
Troutman NC, C.R. Onsrud CNC Manufacturing Plant. Take a tour.
Due to the abrasive and unique structure of composites, it is worth investing in a CNC machine with fully reinforced structural integrity and rigidity. A sturdy design reduces vibrations and tool deflection to provide top acceleration/deceleration speeds, long tool life, and low maintenance and repair costs over the lifetime of the machine compared to less rigid, light-duty machinery. From an upfront cost perspective, a machine can be made cheaper by reducing the structure and quality of its components; however, it will fail to have the longevity of a better built machine and ultimately will result in a higher total cost of ownership.
Large-format Tooling Board Demo. 917 Porsche. Watch now.
In addition to the type of composite material being machined, factor in its size, and select a work envelope accordingly. At a minimum, the work envelope needs to be larger than the largest part being machined. However, depending on production goals, buying a machine with twice the work envelope that supports pendulum processing, where materials are safely loaded/unloaded while the machine is still performing cutting operations on another part, will significantly speed up overall production time. Other advantages of large tables include batch processing which allows you to fixture multiple parts at one time and machine continuously without having to unload and reload.
Note - When searching for 5-axis machining solutions, be sure to consider the work envelope while the machines spindle is at 90 degrees.
M-Series Twin Spindle. Watch the Plastic Machining Demo.
A second spindle is valuable when machining small or long composite parts at high volume. Adding a second spindle doubles the machines throughput without increasing its footprint. Depending on the machine manufacturer, take it a step further by adding up to 8+ spindles for maximum part production.
Similar to a pallet changer for a traditional CNC machine center, a second table allows an operator to load composite material onto, or unload finished parts from, one of the tables while still machining on the other table, so production never has to stop. Additionally, on some machines, two independent tables can be electronically locked together to process extra-large parts.
Dual Process Machining. For High-throughput Production. Watch Video
Dual Process - Combine a multi-spindle option with a multi-table option to unlock the ability to perform what is known as Dual Process machining. With this technology, one spindle performs an operation on one of the tables while the second spindle performs a completely separate operation on the other table, essentially turning one machine into two in the footprint of one machine.
The cost of the CNC machine matters, but more importantly is the return on investment. A cheaper or lesser machine that fails to meet the unique challenges of machining composites and that has to be replaced after only a few years can cost a company more in the long run, not just in direct costs but in lack of part quality, production downtime, program delays, and added frustration. As John Ruskin says, There is hardly anything in the world that some man cannot make a little worse and sell a little cheaper, and the people who consider price only are this mans lawful prey. It is worth the time to work with experts in the field to ensure the machine being purchased is the very best for the specific composites manufacturing application.
C.R. Onsrud Remote Support, Troutman NC.
Asking the right questions provides an understanding of the service and support offered by an original equipment manufacturer (OEM) or dealer. Before making a purchase, some key questions to ask include:
Buying an American-made CNC machine means:
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Comparing CNC machines, wondering which you should buy? In this guide we look at the considerations and options so you make the right choice.
Comparing CNC machines and wondering which you should buy?
Buying a CNC is quite different from buying a 3D printer, or even a laser cutter.
For a start, there is even disagreement on the definitions for what we are talking about, which we will get into in a second.
Secondly, if you have yet to use a CNC, you might not have a clear idea of what you want to do with it.
Third, there are a lot of variables that we need to consider, that might not become clear until having used a machine for real projects, and that are not apparent even after watching and reading reviews.
Keep in mind also, this is not a CNC review, though I will use my own experience of specific machines to inform my thoughts.
Lets get into it.
While most people will have an idea in their head when you say CNC, it simply means it is a fabrication machine under computer control.
That probably serves up more confusion than explaination with that definition alone, both a 3D Printer or a Laser Cutter are CNC machines.
When we speak about CNC, however, we are usually talking about a CNC Mill or a CNC Router.
Both interpret computer instructions to progressively carve out material using a spinning endmill to create our end-product, and therefore this style of production is called Subtractive Manufacture, versus additive in the case of 3D printing.
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So there are two types of machine that people really mean when they say CNC, but how are they different?
CNC Router VsAs you can see in these pictures of machines at Protospace, visually they have a lot in common, but the Mill is set up with a high-torque spindle, and more Z (vertical) + Y (horizontal) travel, whereas the Router is on a moving gantery, and is able to move far further in both the X and Y, with some travel in Z but not anywhere near as much.
Some of the descriptions you hear are applicable to each machine, but if the workpiece moves in all but the up and down (z) direction with the spindle static, it is likely to be a mill.
Mills are more robust, therefore are often used for metal work, or very hard plastics, creating highly precise and repeatable machine parts, for example.
On the other hand, while a router could well cut metal, it would be commonly seen cutting acrylic signs, or in a cabinet maker workshop, cutting and carving MDF drawers and pine doors.
While neither of the above machines would be seen in a home workshop, when we talk about hobbyists, we are almost always talking about a CNC router.
As we have already seen in the use-cases for a CNC mill versus router, different machines are suited to different tasks.
In determining the specific machine you go for, and the budget you ought to expect, you need to know at the very least:
Many people consider CNC routers as being obsolete now that lasers and 3D printing are gaining capabilities, but that is not true yet, and might never be entirely true.
That said, there are many times I consider using a CNC and decide instead to go with 3D printing or laser, just out of comfort and convenience.
Where CNC shines is when you consider materials and scale.
I have a laser that is powerful enough to engrave metal, and can possibly even cut very thin metal, but on my Nomad 3 I can cut and engrave aluminium well, and make pretty decent circuit boards, including cutting them out.
Even with multiple passes I could not cut anywhere close to the thickness of materials that I can cut on my CNC, and there are materials that would be toxic even if I could.
While CNC is subtractive, just as lasers are, it can do 3D using STL files like 3D printers can. This can be useful for simple things like bevels and chamfers, all the way up to intricate 3D carves.
3D test carve of an STL file from Fusion3603D prints are more capable when it comes to shapes, some fine details, and geometry, but CNC is more capable when it comes to size and materials.
As mentioned, there are times I turn to my other digital fabrication options such as 3D printing and lasers over CNC, and here are some reasons:
Ultimately, the decision between a budget CNC and a fifteen thousand dollar machine depends on your specific needs and goals:
Keep in mind that there really is an element of you get what you pay for, but you might be paying for more performance than you need:
All of my home CNC machines run on the open source GRBL software. You can be almost certain yours will too, but Mach 3 and other software is out there and highly popular, especially at makerspaces and manufacturing, so we should touch on this.
GRBL runs on Arduino-based CNC controllers and reads GCcode, much like Marlin in the 3D printer world. This means both the firmware and the hardware can be open and free.
Because it is hugely popular, it offers a wide-variety of software options, including UGS, Chili Pepper, Open Build Control, Carbide Motion, Easel, Cool Term, CNCjs, and more.
Mach3 CNC Software Comparison with GRBLMach 3 is proprietary, and $175 at the time of writing, but does have a limited demo license. It uses your desktop computer and communicates via a parallel port. Yes, it only works on a desktop PC with a parallel port, not a laptop.
While not as beginner-friendly, and of course more expensive, Mach 3 does have advantages in terms of capabilities, for example it can control a 6-axis CNC machine. It also supports macros via scripting, which for a regular hobbyist is not a big deal, but for small-batch manufacturing starts to become interesting.
The three main drive systems on CNC machines are ball screws, rack and pinion, and belt drives.
It is not true any longer that hobbyist machines will always use belts, but it did used to be the case because belts and stepper motors are cheaper, and are easier to manufacture well.
That said, a premium will be paid for more powerful motors and drivers compared to a less expensive machine.
Belts vs ball screwsMy X-Carve 500 has belts, but the belts are sufficient for the work it is expected to do. My Nomad 3 is built more like a mill, it has a smaller, enclosed work area, but uses ball screws.
Ball screws are preferable because belts are stretchy and can cause imperfections due to backlash.
One of the things I liked about my Longmill was even though some of it was not super rigid (eg. 3D printed parts), it used threaded rods instead of belts (but not ballscrews unfortunately).
Ben helping me assemble the LongmillAlmost every entry-level router will use an off the shelf handheld router as its spindle, or a powerful 24v DC motor. In the former case, the speed will be set manually using the dial on the casing, and will be turned on and off manually too.
A premium built CNC will have a specifically designed spindle that features more power and has programmable speed control.
I came to CNC via wanting to prototype circuit boards, because I am scared of nasty chemicals. It was only after owning a machine that I branched out into other things, and eventually took the certification at my makerspace so I could use (and later teach) the big scary Mach3 machines.
This means my machines have almost always been on the smaller size, and my one larger machine as I mentioned earlier, I found I used but didnt really have space for.
My first machine was pretty bare-bones and has many names, but I knew it as T8 CNC. Really, it is just for PCBs, but didnt do a very good job of that because the accuracy and rigidity isnt there. What it did do, at a low price, was take away my fear of the machines.
Next was the Sienci Mill One. Sadly, it is no longer produced, but it was a great machine for me. Again, only small, but much more robust and capable. For a teaching situation it especially proved itself, it was bashed around and abused at the other maker space for a long time and survived.
I tested all kinds of materials on that little guy, and eventually outgrew it. First I upgraded to a slightly larger 500mm x 500mm X-Carve, which I still have and enjoy.
Longmill and X-CarveEventually I upgraded in size again to the Longmill. At the time I got it there was a deal where we got an early version at a discount, so I paid under $2,000 CAD for a 30x30 machine.
Would it have been nice to just lay down a full sheet of plywood or MDF and get cutting? Sure, but even this machine in our two-car garage had to live hung on a wall.
Many of my friends thought I was losing it when I finally (for now) bought a Nomad 3. This machine has a small work area, and can not even accept larger materials because it is all enclosed.
The thing is, it suits 80% of what I use a CNC for, while keeping all the dirt (MDF and carbon fiber especially) and dangerous flying objects mostly inside. When half an endmill goes ping at high speed, that piece of plastic is an eye-saver.
While we had a workshop I was tempted to get a larger machine again, but now we are space-limited I am glad I didnt take the plunge. I just wish there was a makerspace nearby as well-equipped as the ones I left behind in Calgary!
If you are looking to make stuff for yourself, maybe to sell at craft fairs or Etsy, you do not need to be spending $15,000 on a machine like the Avid etc.
While I am a big fan of open source and community, and especially saving money, if this is your first CNC then I would guide you towards one of the well-known brands with a tried-and-tested new customer onboarding:
Both come with free software and work with the popular third party applications, such as Aspire/Vcarve.
For ease of use, I especially like Inventables Easel, which is browser-based, compatible with pretty much any GRBL-based CNC and is free for the basic license. Optionally there is a pro version.
Another option for CNC brands is Onefinity. I have heard good things about these, and they seem comparitively priced, but I have no personal experience of them.
If those are too rich for your budget, then cutting your budget right down to the level where you wont be too upset if it doesnt work out makes sense.
A budget option I have heard good things about is the Two Trees TTC-450, which at the time of writing can be got for under $650 including spindle, but again I havent got any direct experience of this machine.
For me, today if I had the budget and the space, I would likely choose the Shapeoko 5 Pro, because even with VFD, and even though shipping is more than X-Carve, it is still less expensive than the X-Carve Pro.
I dont think you can go far wrong with either the X-Carve or the Shapeoko, though! Would be sure interesting to see them go head-to-head.
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